Bicyce driving mechanism.



No. 64u28.

2 Sheets-Sheet I.

(No Model.)

Nef 64|,728. Patnted 1an. 23, |900.

l T. c. RoBmsoN.

BICYCLE DRIVING MECHANISM.

. (Application filed Feb, 12, 1898.)

trice.

STATES PATENT THOMAS O. ROBINSON, OF MALDEN, MASSACHUSETTS, ASSIGNOR OF ONE- HALF TO E. BAKER WELCH, OF CAMBRIDGE, MASSACHUSETTS.

BICYCLE DRIVING MECHANISNI.

SPECIFICATION forming part of Letters Patent N o. 641,728, dated January 23,1960.

Application filed February 12l 1898. Serial No. 670,019. (No model.)

To @ZZ whom t may concern/.- the lever f is formed with a slot f', in whicli Be it known that I, THOMAS C. ROBINSON, operates a roller c, which is afixed on the of Malden, in the county of Middlesex and -end of the crank-shaft c by means of a shoul- State of Massachusetts, have invented certain dered screw-stud c2. 55 5 new and useful Improvements in Bicycle i is an auxiliary crank aiiixed to thercrankL Driving Mechanism, of which the following shaft c by means of a keyj and formed with is a specification. a slot i', similar to the slot in the lever f and This invention relates to the driving mcchpreferably of equal length. In said slot c" anism of bicycles and similar vehicles; and operates a roller f2, similar to the roller c 'and 6o ro it consists in the novel features of construcaffixed to the inside of the lever f. Dust-caps tion and arrangement, which I shall now prola la, screwed to the crank t' and lever f and ceed to describe and claim. covering the slots in said members, serve to Of the accompanying drawings, forming a protect the parts from dust and other obpart of this application, Figure l represents structions. These dust-caps are removed in 65 15 in side elevation and section a bicycle driv- Fig. l.

ing mechanism constructed in accordance The operation of the device will be readily with myinvention, with parts removed. Fig.V understood. When power is applied to the 2 represents a top plan view and section of pedal g, the said pedal is constrained to rethe same. Fig. 3 represents a perspective volve in a circle Whose center is the center 7o zo view of one of the dust-caps employed. of the eccentric. The pedal istherefore, in The same reference characters indicate the the arrangement shown, at a greater distance same parts in all the figures. from the crank-shaft c on the downstroke Referring to the drawings, d o are the two than it is on the upstroke, and since the lower main-frame bars of a bicycle, c is the crank-shaft is non-rotatively connected with 7 5 2 5 crank-shaft, journaled in ball-bearings c3 o8, the lever f it follows that the torsion exerted and d is the forward sprocket-wheel, affixed on the crank-shaft is greater on the downin the usual manner to the shaft c and constroke, thus giving the rider advantage on nected with the rear wheel by means of a this stroke without enlarging the circle travchain. Any other suitable or preferred deeled by his feet. On the back stroke from 8o 3o vice might of course be used in place of a the position of the parts shown in Figs. l and chain for transmitting power from the crank- 2 the rollers c and f2 are brought near toshaft to the rear wheel. gether at the opposite ends of the slots f e c are eccentrics rigidly affixed to the and 1". frame-bars d b on either side of the machine It will be seen from the foregoingdescrip- 85 3 5 by means of brackets e e', formed with split tion that by means of myinventionlprovidea collars c2 e2, Whichgare clamped to the frame driving mechanism forbicycles and similarveby means of bolts e3 e3. The brackets on the hicles which combines with the advantage in sprocket side are shaped to pass over'and propulsion hereinbefore mentioned strength outside of the sprocket and chain, as'shown. and simplicity, together with adaptability to 9o 4o @.4 c4 are the straps of the eccentrics e c, each Vehicles already in use. In providing a inaof said straps having an arm or crank c5 chine of the ordinary pattern with my deformed on or otherwise attached to it. Bevice no alterations in the frame are necessary, tween the straps and the eccentrics are iny as will readily be understood from the drawterposed antifriction-balls e e, which allow ings and description. 95 45 one part to revolve on the other with the I am aware that it has been proposed'hereminimum of friction. tofore to employ a fixed eccentric in changf is a lever or crank arranged-parallel to ing the leverage in a bicycle crank mechanthe crank e5 and meeting the same at its outer ism, and I do not claim such a construction end, the two being headed or shouldered and broadly. roo

5o joined together by means of the screw-thread- I claimed shaft g of the pedal g. The rear end of l. In a mechanism of the character described, in combination, a crank-shaft, an eccentric afxed to the bicycle-frame and having a strap, a lever carrying at its outer end the pedal-shaft and formed with a slot in its inner end, a pivotal connection `between said lever and the eccentric-strap, a roller attached to the crank-shaft, and forming a fulcrum for said lever, an auxiliary crank secured to the crank-shaft and formed with a slot, and a roller attached to the lever and operating in said slot.

2. In a mechanism of the character described, in combination, a crank-shaft, an eccentric afxed to the bicycle-frame, an arm or crank attached to the strap of said eccenl i i 

